A ball-grid array (BGA) package is an illustrative example of a surface-mount package for an integrated circuit chip. Ball-grid array (BGA) packages house an integrated circuit (IC) chip that is either wire-bonded or flip-chip mounted to bond pads on the surface of an interposer. The interposer is generally a small circuit board or a semiconductor package for interfacing a circuit board.
In high-speed digital applications, electrical interconnections associated with the chip, the interposer, and the board interconnections of a BGA can exhibit electrical resonances and reflections that degrade signal integrity and electrical system reliability. Such degradations of signal quality generally increase with increasing signal frequencies or with digital signals that exhibit short rise times. Moreover, if power supply voltages are decreased to save energy, the detrimental affects on signal integrity may increase because of lowered electrical noise immunity.
In the past, discrete resistors have been placed in the signal path to reduce or eliminate unwanted resonances and signal reflections. However, additional cost, weight, assembly complexity, and reduced circuit density are incurred with the use of discrete resistors. Thus, a need exists for a resistor or a passive component which can reduce signal reflections for high-speed digital applications while meeting cost and circuit density objectives.